Im sure they do. Plenty of every episode on youtube or their was so all would survive.
Yeah well I have heard that they just kept the important footage such as the episodes and then got rid of the stuff they didn't need such as outtakes and unused scenes, but I would like to see these from Series 1 and 2 if any survive, which they possibily do, if not in the BBC archives then in someone's home who worked behind the scenes on the original series. It is more likely that the newer series outtakes still exist because of the possibility of usage on the end credits. John Sayle, writer on the series, did tell me that only some of the outtakes were kept for the end credits and the rest were scrapped, but who knows, he did say he wished many of them were still around because they were really funny and had a great time making them and watching them. The earliest I have seen are two from Series 9 that appeared on 'Aunties Bloomers.'